The present invention relates to a resin-encapsulated package (hereinafter referred to simply as xe2x80x9cplastic packagexe2x80x9d) formed by sealing a semiconductor IC chip in a plastic molding. More particularly, the present invention relates to a plastic package having a small size and facilitating package mounting work, a lead member for the plastic package, and a method of fabricating the lead member.
Recently, the level of integration of semiconductor IC chips has progressively risen, techniques for device miniaturization have advanced and abilities of electronic equipment have been enhanced, and the miniaturization of semiconductor IC chips is the trend of the times. As represented by the development of ASICs, further increase in the number of components per chip and further improvement in performance are desired.
Activities for the development of plastic packages employing a lead frame trend from those for the development of surface-mount packages, such as SOJ packages (small outline J-leaded packages) and QFPs (quad flat packages), via those for the development and miniaturization of thin, small plastic packages, such as TSOPs (thin small outline packages) toward those for the development of LOC packages (lead-on-chip packages) to improve packaging efficiency through the three-dimensional arrangement of components in a package.
Further increase in the number of pins, further thickness reduction and further miniaturization have been required of plastic packages in addition to increase in the number of components and functional enhancement. A limit for the miniaturization of the conventional packages has come into view due to restrictions on the arrangement of leads around chips.
The present invention has been made under such circumstances to miniaturize a plastic package by increasing the ratio of the size of a semiconductor IC chip to the package size of the plastic package including the semiconductor IC chip and to provide a plastic package requiring a small area on a wiring board to increase plastic package mounting density on a wiring board.
According to the present invention, a plastic package having terminals including some exposed terminals includes: a semiconductor IC chip sealed in a resin molding, and a lead member having an arrangement of a plurality of discrete terminal sections; wherein each of the terminal sections has inner terminal parts to be electrically connected to terminals of the semiconductor IC chip, outer terminal parts to be connected to external circuits, and connecting parts interconnecting the inner and the outer terminal parts, the inner and the outer terminal parts are formed such that the contact surfaces of the inner terminal parts and those of the outer terminal parts face toward opposite directions, respectively, the inner terminal parts and the connecting parts are thin, and the outer terminal parts are thick, the contact surfaces of the inner terminal parts of the terminal sections are flush with each other, a terminal-side surface of the semiconductor IC chip on the side of the terminals faces a surface of the lead member on the side of the contact surfaces of the inner terminal parts, the terminals of the semiconductor IC chip are joined to or in contact with the contact surfaces of the inner terminal parts of the lead member, and the terminals of the semiconductor IC chip are connected electrically to the inner terminal parts of the lead member.
In the plastic package, the terminals of the semiconductor IC chip are provided with protruding electrodes, and the protruding electrodes are joined to or in contact with the contact surfaces of the inner terminal parts.
In the plastic package, the contact surfaces of the inner terminal parts are coated with connecting plated metal layers, respectively, and the terminals of the semiconductor IC chip and the inner terminal parts of the lead member are connected electrically through the plated metal layers, respectively.
In the plastic package, the plated metal layers are at least plated solder layers, plated gold layers, plated silver layers or plated palladium layers.
In the plastic package, the plated metal layers are formed on only parts of the contact surfaces of the inner terminal parts facing the terminals of the semiconductor IC chip.
In the plastic package, the contact surfaces of the inner terminal parts are coated with a conductive paste layer, the terminals of the semiconductor IC chip and the inner terminal parts of the lead member are connected electrically through the conductive paste layer.
In the plastic package, at least portions of the outer terminal parts are exposed on the resin molding or external electrodes of solder or the like are formed on the surfaces of the exposed portions of the outer terminal parts.
A lead member according to the present invention for a substantially flat plastic package including a semiconductor IC chip includes a plurality of discrete terminal sections, and a frame surrounding and holding the plurality of discrete terminal sections, wherein each of the terminal sections has inner terminal parts to be electrically connected to terminals of the semiconductor IC chip, outer terminal parts to be connected to external circuits, and connecting part interconnecting the inner and the outer terminal parts, the inner and the outer terminal parts are formed such that the contact surfaces of the inner terminal parts and those of the outer contact parts face toward opposite directions, respectively, the inner terminal parts and the connecting parts are thin, the outer terminal parts are thick, contact surfaces of the inner terminal parts of the terminal sections are flush with each other, the frame is provided with supporting parts other than the connecting parts, and the supporting parts are connected to the outer terminal parts, respectively.
Preferably, the lead member is formed by processing a metal sheet by a half-etching method.
In the lead member, the contact surfaces of the inner terminal parts are coated with connecting plated metal layers, respectively, and the terminals of the semiconductor IC chip and the inner terminal parts of the lead member are connected electrically through the plated metal layers, respectively, when assembling the lead member and the semiconductor IC chip.
In the lead member, the plated metal layers are at least plated solder layers, plated gold layers, plated silver layers or plated palladium layers.
In the lead member, the contact surfaces of the inner terminal parts are coated with conductive paste layers, respectively, the terminals of the semiconductor IC chip and the inner terminal parts of the lead member are connected electrically through the conductive paste layers, respectively.
In the lead member, the paste layers are formed of a Pb-free paste.
In this specification, the term xe2x80x9chalf-etching methodxe2x80x9d signifies an etching method including a half-etching process.
A method of fabricating a lead member as described above includes the step of processing a metal sheet by a half-etching method so that the surfaces of the inner terminal parts, the connecting parts and the supporting parts are portions of one of the surfaces of the metal sheet, the inner terminal parts, the connecting parts and the supporting parts have a thickness smaller than that of the metal sheet, and the outer terminal parts have a thickness equal to that of the metal sheet.
In the lead member fabricating method, plated metal layers are formed on the contact surfaces of the inner terminal parts, respectively.
The plated metal layer is formed by coating the surface of the lead member with a photoresist film, patterning the photoresist film to form openings in parts thereof corresponding to the contact surfaces of the inner terminal parts so that the contact surfaces of the inner terminal parts are exposed, and subjecting the lead member to a plating process using the patterned photoresist film as a mask to plate the exposed contact surfaces of the inner terminal parts.
In the lead member, the contact surfaces of the inner terminal parts are coated with paste layers, respectively.
In the lead member, the paste layers are formed by a printing method or a dispense method.
The plastic package of the present invention increases the ratio of an area occupied by the chip to the package size of the plastic package to miniaturize the plastic package. Thus the plastic package can be mounted on the wiring board in a small area to increase plastic package mounting density on the wiring board.
A ball grid array type plastic package can be formed by forming the outer electrodes in solder balls on the outer terminal parts.
More concretely, a lead member is formed by individually arranging a plurality of terminal sections each having thin inner terminal parts connected to the terminals of a semiconductor IC chip, thick outer terminal parts to be connected to an external circuit, and thin connecting parts interconnecting the inner and the outer terminal parts so that the contact surfaces of the inner terminal parts thereof face toward the same direction and extend flush with each other. The contact surfaces of the inner terminal parts and the contact surfaces of the outer terminal parts face toward opposite directions, respectively, and a surface of the lead member on the side of the inner terminal parts and a surface of the semiconductor IC chip on the side of the terminals face each other. The terminals of the semiconductor IC chip are joined to or in contact with the contact surfaces of the inner terminal parts of the lead member on the side of the terminals, and the terminals of the semiconductor IC chip are connected electrically to the inner terminal parts of the lead member.
The surfaces of the outer terminal parts protrude beyond the inner terminal parts and the connecting parts on a side of the lead member opposite a side on the side of the semiconductor IC chip, the surfaces of the outer terminal parts can be formed two-dimensionally in a plane parallel to the surfaces of the terminals of the semiconductor IC chip. Even if the number of the terminals of the semiconductor IC chip is increased and the pitches of the terminals are reduced, mounting on a practical level is possible.
In other words, further increase in the number of the pins of a plastic package can be achieved.
The CSP (chip size package) having a resin molding of dimensions substantially corresponding to the external dimensions of the semiconductor IC chip can be formed in a small size.
The plastic package can be formed in a small thickness and is satisfactory in heat dissipating performance when the outer terminal parts thereof are formed such that parts of the contact surfaces and side surfaces thereof are exposed.
The terminals of the semiconductor IC chip are arranged on a middle line between the opposite sides of the contact surface of the semiconductor IC chip, and the inner terminal parts of the lead member are arranged on lines extending in parallel to the middle line on the opposite sides of the middle line, respectively. Thus the plastic package is simple in construction and suitable for mass production.
The lead member of the present invention to be incorporated into the plastic package of the present invention can be formed by an ordinary etching method employing a half-etching process.
The lead member fabricating method of the present invention is capable of comparatively easily fabricating the lead member by the half-etching process and, consequently, the plastic package of the present invention can be fabricated.